PHOENIX (AP) – Federal authorities are investigating the deaths of two free-roaming horses found shot on national forest land in eastern Arizona.

U.S. Forest Service investigators discovered the dead horses near Heber-Overgaard in the Apache-Sitgreaves National Forests after receiving a tip last month, The Arizona Republic reported.

The horses could not be confirmed as belonging to the federally protected Heber herd, but investigators are treating them as such, said Jean Nelson-Dean, a representative of the Forest Service Southwest region.

U.S. law prohibits killing a wild or free-roaming horse on federal lands. All unbranded and unclaimed horses on public lands fall under the protection.

Horse wrangler Robert Hutchison discovered the dead horses and reported them to authorities. The two carcasses were about 20 yards apart, he said. One of the horses appeared to have multiple gunshot wounds.

A group of live horses were staying near the bodies when Hutchinson photographed the scene.

"They were mourning the way we mourn the loss of loved ones," Hutchison said.

Authorities have not yet uncovered a motive for the shootings. The Navajo County Sheriff's Office is offering a $2,500 reward for information leading to the arrest and conviction of those involved.

In recent years, authorities have investigated several shootings involving free-roaming horses in Arizona.

The Navajo County Sheriff's Office began an investigation in May 2017 after two wild horses were found dead on Forest Service Roads 50 and 51. The three-month investigation led to a search warrant being issued, but investigators were able to obtain enough evidence to make an arrest, said Randy Moffitt, chief deputy of the sheriff's office.

In October 2016, a foal was killed outside Phoenix. A witness told authorities that a person was shooting horses of the Salt River herd in eastern Maricopa County. The shooter wounded three horses, killing one, the Maricopa County Sheriff's Office said.

Five months before the shooting, Arizona Gov. Doug Ducey signed a bill protecting Salt River horses, which mostly live in the Tonto National Forest but are not federally protected. The horses are considered feral, domestic horses that were abandoned or have escaped from their owners.

Some ranchers and residents see the horses as pests, claiming their unchecked populations compete with livestock.